Overview
This lecture covers diffusion, explaining its definition, how it applies to cell membranes, and the factors that affect its rate.
What is Diffusion?
- Diffusion is the net movement of particles from an area of higher concentration to an area of lower concentration.
- The process occurs because molecules naturally move randomly and spread out over time.
- Net movement describes the overall movement of all particles in a group, not just individual movements.
- Diffusion can occur in both gases (e.g., perfume spreading in a room) and liquids (e.g., food coloring in water).
Diffusion and Cell Membranes
- Diffusion can happen through partially permeable cell membranes, allowing only certain molecules to pass.
- Small molecules like water, glucose, and amino acids can diffuse through cell membranes.
- Large molecules such as proteins and starch cannot pass through due to their size.
- Diffusion is a passive process, requiring no energy from the cell.
Factors Affecting Rate of Diffusion
- The concentration gradient is the difference in concentration between two areas; a larger gradient increases the diffusion rate.
- Temperature affects rate; higher temperatures make particles move faster, increasing diffusion rate.
- Surface area impacts diffusion; a larger surface area allows more particles to diffuse at once, increasing the rate.
Key Terms & Definitions
- Diffusion — Net movement of particles from high to low concentration areas.
- Concentration Gradient — Difference in particle concentration between two areas.
- Partially Permeable Membrane — A barrier that allows only certain molecules to pass through.
- Passive Process — A process that does not require energy input from the cell.
Action Items / Next Steps
- Review the definitions and factors affecting diffusion for upcoming quizzes.
- Be prepared to give examples of diffusion in daily life and within cells.